title: Gray matter differences contribute to variation in cognitive performance in Parkinson's disease.
abstract: OBJECTIVE
  A substantial proportion of patients with Parkinson's disease (PD) suffer from cognitive deficits, although there is a large variability in the severity of these impairments. Whilst the cognitive deficits are often attributed to monoaminergic changes, there is evidence that alterations in structural brain volume also play a role. The aim of our study was to gain more insight into the variability of cognitive performance amongst PD patients by examining the relation between regional gray matter (GM) volume and cognitive performance.
  
  
  METHODS
  Linear regression analyses were performed between task performance and GM volume for six neuropsychological tasks within a group of 93 PD patients; they were additionally compared at a group level with matched healthy controls, using voxel-based morphometry.
  
  
  RESULTS
  Our most important findings were positive correlations between GM volume and cognitive performance for (i) parahippocampal gyrus and verbal memory, (ii) medial temporal lobe and putamen and visuospatial memory, and (iii) middle temporal gyrus and frontal lobe and verbal fluency. In addition, decreased GM volume was found in the frontal, parietal and temporal cortices of PD patients compared with matched healthy controls.
  
  
  CONCLUSIONS
  It is argued that the large variability in cognitive function across PD patients is partly mediated by GM volume differences in the implicated areas. Volume differences in these brain regions do not discriminate between patients and controls but explain cognitive variation within the patient population.
authors.affiliation: Department of Anatomy and Neurosciences, VU University Medical Center (VUmc), Amsterdam, The Netherlands.
authors.forename: N J H M
authors.initials: NJ
authors.lastname: Gerrits
authors.forename: Y D
authors.initials: YD
authors.lastname: van der Werf
authors.forename: M
authors.initials: M
authors.lastname: Hofman
authors.forename: E M J
authors.initials: EM
authors.lastname: Foncke
authors.forename: M
authors.initials: M
authors.lastname: Klein
authors.forename: H W
authors.initials: HW
authors.lastname: Berendse
authors.forename: O A
authors.initials: OA
authors.lastname: van den Heuvel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology*; D003071:Cognition / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D036421:Nerve Fibers, Unmyelinated / Q000473:pathology*; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000473:pathology* / Q000523:psychology
keywords: Parkinson's disease; cognitive deficits; structural MRI; voxel-based morphometry